For the maintenance of fueled devices such as aircraft, and the safety of passengers and flight crew, it is known to periodically test for the presence of contaminants in a fuel line. One such contaminant is water that may have entered the fuel line and contaminated the fuel.
Often aircraft have a quick-release or other type of valve, positioned on the underside of one or both wings or on another location of the aircraft, from which a sample of fuel from the fuel tank or fuel line may be collected. A fuel sample may be collected in a vessel, such as a clear plastic body, and then tested for the presence of contaminants such as water. One form of testing includes using a float with a density greater than fuel but less than water. The float is placed in a collection vessel and a sample of fuel is collected in the vessel. If there is water present in the fuel, the water will form a separate phase or layer at the bottom of the vessel. The fuel will form a layer above the water in the vessel. The float will sit at the interface between the water and fuel thereby indicating to the user that water is present in the fuel sample, and thus the fuel line or tank may be contaminated.
Another form of testing for the presence of contaminants in a sample of fuel uses a filter element. The filter element typically is positioned in a vessel, such as a clear cylinder, thereby dividing the vessel into an upper chamber and a lower chamber. A sample of fuel is collected in the upper chamber. The filter element may be formed of a selectively-permeable material which blocks the flow of one or more contaminants, e.g. a hydrophobic material that blocks water, and is permeable only to fuel. In that example, the fuel will pass through the filter element into the lower chamber and any contaminant present in the sample will remain in the upper chamber thereby visually alerting the user to the presence of the contaminant.
Testing for the presence of contaminants such as water in a fuel sample can be time consuming. Further, convenient testing or inspection of fuel samples should be available immediately on taking the sample, regardless of the surrounding conditions. While instruments have been developed to detect water in a fuel sample, there remains a need to determine quickly and accurately whether such contaminants are present in a fuel sample in any environment.